To dispose of infectious waste from hospitals or the like, use has primarily been made heretofore of incinerator installations which may be remote from the hospital and to which the waste may be trucked. The use of open trucks for carrying infectious waste poses a significant problem to people along the path and is barred by regulations or laws for the most part. As a consequence, it has been necessary to provide incinerators on the hospital property which takes up space normally more desirable for other purposes. Some of the incinerators have been in use for decades and can be operated only at high cost and may not be capable of fully decontaminating the infectious waste or may not be sufficiently environmentally sound under present day regulations and statutes.
To minimize the danger to the environment and save costs, it has been proposed to provide disinfection plants in which the hospital waste is so treated that it can be thereafter transported like conventional household waste and treated in a similar manner, e.g. by disposal on a landfill or incineration in a municipal incinerator. It has also been proposed to provide vehicular disinfection plants which can so disinfect the waste that it can be handled like household waste and which can service a number of hospitals.
One system utilizing a vehicular disinfection system in which a charging shaft is provided on a vehicle chassis is described in EP-A2 0 277 507. In this apparatus, the disinfection is effected by heating the shell of the conveyor worm so that the latter forms the disinfection stretch of the path of the waste. A mixture of air and steam is drawn off at the end of the worm conveyor and is passed into the atmosphere after traversing an active carbon filter. The vehicle bed is a trailer of a semi-trailer vehicle in which a tractor is overhung by an end of the trailer.
In the worm conveyor, the material transported thereby is in the form of a loose bulk which is only turned or disturbed to a small extent. Particles within the interior of the bulk material may have little or no intensive contact with the treatment gas (e.g. superheated steam or some other sterilizing medium) and such interior particles tend to be shielded from the heated wall surfaces of the conveyor by the surrounding material.
This drawback is greater, the larger the cross-section of the bulk material movement through the conveyor. A uniform heating of all particles in such a system can only be achieved with very small conveyor cross section and long residence times. This, of course, reduces the throughput. With mobile apparatus, by contrast, the economies of the system require at each pickup location, all of the waste pass through the plant in the shortest possible time and be thoroughly disinfected so that the largest possible number of locations can be serviced by the vehicle.
German Patent 37 05 364 describes another disinfection plant in which the disinfection stretch is also formed by a conveyor worm. This system differs from the first-mentioned system in that the gaseous treatment medium flows in a closed path, i.e. is recirculated and within the conveyor flows in concurrent flow with the waste material to be treated, i.e. in the same flow direction as the waste.
Mention may also be made of German Patent Document DE-OS 25 05 185 from which it is known to disinfect infectious waste continuously utilizing hot air or superheated steam as the disinfection medium in a rotary tube or rotary kiln. Prior to or during this disinfection a comminution is effected and a compactor or press is provided to reduce the volume, at the downstream side of the rotor kiln.